type 4 tinware non-return flap covers

[T1 Terry]

Your bus, do what you like…….
however, if there are fumes in the warm air, you have an exhaust leak and or oil dripping onto the heater boxes…..both can be fixed.
Kombi heaters, in my experience are toasty warm on cold days and operate efficiently if everything has been maintained to spec……..including the booster fan.
(….and to the best of my knowledge, the flaps that Darren refers to aren’t part of the heating system…….)
Just sayin’

I believe the job of those flaps is to pump some air through the heater boxes and when the heater flaps are closed, that air goes out through the bypass section under the heater flap cover I believe, but I can't find an example in amongst my kombi parts pile .... mostly because it's been there for the 7 yrs since we arrived in SA and still hasn't been sorted, but rather other stuff has been piled there as well 

The smell problem wasn't so much an oil smoke or exhaust fume problem, but they were there along with the baked dirt smell. Our Kombi has a lot of kms on the clock and a lot of those were off the bitumen. I think previous owners had simply left the connector/muffler tubes off but not sealed the transfer tubes that bring the hot air up front. This caused dust to be pulled up inside those tubes and then baked on with oil mist that the "forever" oil leak from one of the previous engines ...... 

When Kombi has its EV conversion, it will have a reverse cycle air conditioner plumbed into the existing system as well as one of those fibreglass manifold things that the after market air con people made to go in the roof cavity of the cab.

T1 Terry